Within the context of high-resolution imaging methods, such as computer tomography in medical imaging, X-ray detectors are usually used to generate a high-resolution spatial image of an area of a patient under investigation.
In this context, an X-ray detector whereof the sensor layer takes the form of a directly converting semiconductor layer enables the quantitative and energy-selective detection of individual X-ray quanta. At the incidence of X-ray radiation, electron-hole pairs—that is to say pairs of negative and positive charge carriers—are generated in the sensor layer. As a result of voltage applied at the sensor layer or at the surface of the sensor layer, the charge carriers are separated and move towards the electrodes, or the surfaces of the sensor layer, of the respectively opposite charge. The current caused thereby, or a corresponding charge transfer, can be evaluated by downstream sensor electronics. Semiconductor materials in the form of CdTe, CdZnTe, CdTeSe, CdZnTeSe, CdMnTe, GaAs, Si or Ge that have a high absorption cross section for X-ray radiation are for example suitable for detecting X-ray quanta.
In particular in computer tomography, large-area X-ray detectors are required, and for this purpose a plurality of comparatively small detector modules are frequently used. Such detector modules in turn comprise individual sensor boards that are arranged adjacent to one another on a common module carrier at the smallest possible spacing (˜100 μm) and whereof the sensor layers together form the sensor surface of a detector module.
Subdividing the sensor surface of a detector module by using mutually adjacent sensor boards enables, in particular, controlled scaling and, if the entire surface is used, also an increase in the signal yield of a detector. For this purpose, a sensor board usually includes a desired number of mutually adjacent hybrids arranged on a carrier. A hybrid itself comprises a sensor layer that is mounted on a certain number of reader units such as ASICs.
In the case of conventional scintillator-based sensor boards, the components are secured to one another in conventional manner by way of an adhesive procedure. For this, there is known from DE 10 2011 079 389 B4 a method (and analogously a device) that is suitable for filling, without overspill, a gap between a carrier and a component that is fixed to the carrier with an initially liquid adhesive. In the context of the method, which may be used for example when manufacturing detectors for the detection of X-ray and gamma radiation, such as in computer tomography equipment, an outlet aperture of a line connected to a reservoir is arranged at the peripheral edge of the gap.
The liquid adhesive in the reservoir then flows out of the outlet aperture directly into the gap and fills the latter, by way of capillary forces. The outlet aperture is only detached from the peripheral edge of the gap once the adhesive in the filled gap has cured and so can no longer flow, with the result that no material residue remains in the form of an overspill jutting beyond the peripheral edge of the filled gap.
In the case of quantum counting X-ray detectors, also called photon counting X-ray detectors, and the correspondingly used sensor boards, securing of the sensor layer on a respective number of reader units is usually performed by way of solder elements, so-called “bump bonds”, by which the components to be connected are secured to one another. When manufacturing a hybrid for a sensor board of this kind, the solder elements are applied to the surface of the reader unit that faces the sensor layer in the assembled condition, and then the reader unit is brought into contact with the sensor layer by way of the solder elements. Subsequently heating the solder material connects the components to one another.
In a method of this kind, too, a gap is formed between the components that, for the purpose of improving mechanical stability and thermal conductivity between the components, has to be filled with an appropriate material, in particular an electrically insulating and thermally conductive material.
It is always a crucial challenge with a filling procedure of this kind, the so-called “underfill” procedure, to avoid material residues, caused by manufacture, on the peripheral edge of the manufactured sensor board or in general the components used in the context of manufacturing a sensor board.
In the context of filling, hitherto it has only been possible to make “classic” 1:1 hybrids each having one reader unit per sensor layer. Manufacture of so-called multi-hybrids (1:1, 1:2, 1:3 or 1:4 hybrids), which include a plurality of reader units per sensor layer, can only be performed by way of such a method at the expense of undesired impairment of the detector efficiency, since in this case material residues are formed in the intermediate edge regions of the components.
It is not possible to perform manufacture of sensor boards having a plurality of multi-hybrids (multi-hybrid sensor boards), since the gaps between the reader units of the hybrids also have to be filled with the filling material that is used. As a result, the individual sensor layers of the respective hybrids are coupled mechanically to one another, as a result of which the natural voltage of the sensor material is increased and thus the performance and efficiency of the respective X-ray detector is impaired.